DP Chemistry (first assessment 2025)
Question 21M.2.HL.TZ2.b(ii)
| Date | May 2021 | Marks available | [Maximum mark: 1] | Reference code | 21M.2.HL.TZ2.b(ii) |
| Level | HL | Paper | 2 | Time zone | TZ2 |
| Command term | Calculate | Question number | b(ii) | Adapted from | N/A |
b(ii).
[Maximum mark: 1]
21M.2.HL.TZ2.b(ii)
Calculate the change in entropy, ΔS, in J K−1, for the decomposition of calcium carbonate.
[1]
Markscheme
«ΔS = (40 J K−1 + 214 J K−1) − (93 J K−1) =» 161 «J K−1» ✓
Ignore an extra step to determine total entropy change in JK–1: 161 J mol–1K–1 x 5.55 mol = 894 «J mol–1K–1»
Award [1] for 894 «J mol–1K–1».
Syllabus sections
Reactivity 1. What drives chemical reactions? » Reactivity 1.2—Energy cycles in reactions » Reactivity 1.2.4—An application of Hess’s law uses enthalpy of formation data or enthalpy of combustion data to calculate the enthalpy change of a reaction. Calculate enthalpy changes of a reaction using ΔHf⦵ data or ΔHc⦵ data: ΔH⦵ = Σ ΔHf⦵products − Σ ΔHf⦵reactants ΔH⦵ = Σ ΔHc, ⦵reactants − Σ ΔHc. ⦵products